1. Field of the Invention
This invention relates to wireless systems and more particularly relates to self-configuring wireless systems.
2. Related Art
This application is related to U.S. Pat. No. 5,404,574 to Mathilde Benveniste, entitled “Apparatus And Method For Non-Regular Channel Assignment In Wireless Communication Networks”, assigned to AT&T Corporation and incorporated herein by reference.
This application is also related to U.S. Pat. No. 5,787,352 to Mathilde Benveniste, entitled “System And Method For Management Of Neighbor-Channel Interference With Power Control And Directed Channel Assignment”, assigned to AT&T Corporation and incorporated herein by reference.
Growing demand for wireless voice and data communications will soon lead to a complex mixture of cells, found in unpredictable signal propagation environments. Easy installation and readiness for operation are features that appeal to an owner/operator of a wireless communication system based on a channelized air interface. Examples of such air interfaces include the Advanced Mobile Phone Service (AMPS), the Interim Standard 136 (IS-136), the Global System for Mobile Communications (GSM), and the EDGE interface. Radio frequency (RF) planning for such systems is difficult and expensive to do manually and is becoming a more substantial portion of wireless communication costs as the cost for base stations decreases. Ideally, one would want wireless systems that can self configure. Once the base stations are in place, the system would have the ability and intelligence to perform all RF-planning tasks autonomously.
The ultimate goal of self-configuration is to delegate all RF planning tasks, presently performed manually by expert staff, to software residing within the wireless system. In addition, a wireless system should be self-healing, and it should scale up easily without the need for major service disruption and complete re-planning. Finally, in addition to totally automating RF planning, self-configuration should also put in the hands of the owner of a wireless system—however large or small—optimal algorithms for every aspect of RF planning. For all this to be achieved, a self-configurable system must be able to extract, from data it collects itself, the necessary information to support its software intelligence.
The key RF-planning tasks facing operators of wireless channelized systems are the following: the construction of neighbor lists, power planning, and re-use planning. The neighbor list facilitates hand-over to neighbor cells of calls made by moving subscribers. Power planning addresses two problems: setting the transmit-power levels on the control channel and on the traffic channels. The relative power transmitted on the various base stations' control channels determines cell coverage. Traffic power control is intimately linked to traffic channel assignment as the transmitted power determines interference.
Re-use planning, the system-planning task that has received most attention in the literature, addresses three distinct problems. One is the assignment of frequencies/time slots to the control channels of base stations. Another re-use planning task is traffic-channel assignment, which assigns frequencies/time slots to voice calls or packets as they occur. The third re-use planning task, which arises only in hierarchical configurations, deals with the sharing of the same RF spectrum by two wireless systems. [1] Supporting re-use planning, are the channel ‘re-use criteria’ which have traditionally taken the form of ‘interferer lists’, comprising the cells capable of causing interference if assigned the same channel. An interferer list is similar to a neighbor list, except that it involves different threshold values. The same method thus applies to the derivation of both.
A problem confronting the prior art is how to derive re-use criteria to assign channels to cells in a wireless communications system, based entirely on measurements made by the system during normal operation, thus enabling self-configuration.